Fiancés family HATES me

a33

I’m not sure why my fiancé’s family hates me. I’ve never been disrespected. I’ve always been there for them. His niece sees it and we talked about it and she’s always around. She says she doesn’t understand either but it’s happened with previous girlfriends of his.. we have a baby together and all. I try to be there as much as possible. But they hate me no matter what I do.